I am a birder from Maryland in the USA, just returned from a trip to Slovenia. While there, in the area near Lesce/Lake Bled, I observed two large raptors soaring. I did not have binoculars with me at that moment, and so all I can tell you is that they were brownish overall, with dark primaries and white "windows" just inside the primaries that reminded me of those on a Red-shouldered Hawk here in the USA.
My Slovenian hosts didn't know the English name for them. They told me the birds weren't any kind of eagle, and the Slovenian name sounded something like ken-yeh. In looking at this site, the closest I've seen is the Rough-legged Buzzard, but I don't know how common they are or how likely they would be for this ID.